1. Field of the Invention
The present invention generally relates to electrical safety apparatus and more particularly relates to a removable protection cover.
2. Description of the Prior Art
It is common in the design and fabrication of electrically operated devices to protect various electrical circuits using overcurrent protection fuses. For industrial applications involving a large number of heavy current, high voltage circuits, power distribution panels are used to accommodate the overcurrent protection fuses. U.S. Pat. No. 4,870,542 issued to Koslosky et al, shows an approach to a power distribution panelboard.
Holders for the individual fuses are concerned with obtaining low resistance contact between the fuse and the corresponding electrical circuit. U.S. Pat. No. 4,568,137 issued to Leuthold; U.S. Pat. No. 4,962,363 issued to Sexton; U.S. Pat. No. 4,968,264 issued to Ruehl et al; U.S. Pat. No. 4,872,262 issued to March; U.S. Pat. No. 4,941,851 issued to Hsueh; U.S. Pat. No. 4,944,691 issued to Marach; and U.S. Pat. No. 4,966,561 issued to Norden each describe a slightly different approach to apparatus for holding the various types of fuses.
A common concern, particularly when higher voltages are present in the circuit, is protection of the operator and maintenance personnel from contact with the electrically conductive portions of the fuse holder. Ordinarily this involves a device attached to the fuse holder which encases the entire fuse assembly. U.S. Pat. No. 4,938,715 issued to Jones et al, shows such a device. Because the cover attaches to the fuse block, it is a relatively complex structure which is only useful for the specific fuse block for which it is made.
U.S. Pat. No. 4,721,862 issued to Cooper shows an improved fuse cover which covers a number of fuses within a fuse block. Because of the attachment to the fuse block, however, the Cooper approach restricts use of the cover to the specific fuse block. A second problem with attachment to the fuse block is that the cover tends to constrict movement of cooling air. Particularly in high current electrical circuits, this may prove to be a problem. The solution of supplying cooling air to individual fuses tends to be complex and costly. U.S. Pat. No. 4,921,451 issued to Carlson uses a hinged cover. Note that it is also attached to the fuse holder and therefore has the above identified problems.
A fuse cover attached to the individual fuse is shown in U.S. Pat. No. 4,926,290 issued to Mizerak. The corresponding use of the fuse cover with a fuse holder is shown in U.S. Pat. No. 4,841,413 issued to Mizerak. Because the cover is attached to the fuse, it is useful with a wide range of fuse holders. However, like the covers attached to the fuse holder, the Mizerak cover encircles the fuse. Therefore, even though the ends of the cover are open, it tends to disturb air movement in any direction not longitudinal to the fuse. The fuse covers are individually placed over each fuse requiring all fuses to have a cover to provide adequate protection.